System for parallel operation of motors



Jan. 5, 1932. J. 1 FlNcH 1,839,385

SYSTEM FOR PARALLEL OPERATION OF MOTORS Original Filed Feb. 3.65l 1935 IIL INVENTQR Q Mss L. FINCH BY d6( a/I/pcc TTORNEY Patented Jan. 5, Y 1932 UNITED STATES PATENT orricr.

JAMES L. FINCH, or NEW YORK, 4N.` Y., AssI'GNoR To RADIO CORPORATION or AMERICA,

f A CORPORATION or DELAWARE y SYSTEM FOR PARALLEL OPERATION OF MOTORS Application led February 176, 1925, Serial No. 9,536. Renewed December 28, 1929.

The invention concerns an arrangement for parallel Operation of driving motors for alternators. Y y

One object of the invention isl to provide for steady operation of induction motors for driving alternators connected in parallel.

Another object of the invention is to provide for paralleling the primaries and secondaries ofinduction motors to give constant and equal speeds to the rofatingelements and thus provide for synchronous operation.

Still another object of the invention is to provide for p aralleling the primaries and secondaries of induction driving motors having regulating resistances in the secondary circuits partially common to all phases of the secondaries and partially individual to each phase. A f

In the operation of high frequency alternators inparallel for feeding the antenna of a modern high power radio transmission station it has been found desirable to provide a paralleling connection for both the primaries and secondaries ofthe driving motors in the usual installation. A plurality of rheostats are ordinarily connected in the secondary circuit to regulate the motor speed. The paralleling connection of the secondaries is connected ahead of these resistancesand, therefore, each of these resistances affects the circuit characteristics of both motors. It is known that the impedance characteristics of the secondary of an in duction motor vary considerably at different positions vof the secondary and, therefore, as the motor rotates there is a constantly varying impedance and consequently a constantly varying circulating current in the tie circuit between thesecondaries. AThese impedance characteristics termed a smoothing resistance in each motor secondary line ahead of the tie circuit. Such a resistance, of course, modifies the circulating current in each lme and its effect on the circulating current is much greater than the effect of theinternal impedance of the secondary windings. The instantaneous changes in the impedance of the windings of the motors will, therefore, have `little effect as compared to the effect of the resistances on the circulating current and this 'circulating current will have substantially equal values in all positions of the motor secondary. The slight difference in the internal circuit constants of the rotors thereupon becomes unimportant and the tendency to hunt is greaty andare driven by induction motors M and M1. The connections on the two sides of the figure are identical and it is, therefore, necessary to explain only those to the left of the figure including the motor andthe generator G. This motor comprises a primary winding l and a secondary Winding 2. The primary l is energized from the three phase lines 8, 9 and 10 each including saturation coils indicated diagra-mmatically at 40. l The saturation of the cores of these coils is varied by saturating coils connected to the direct current generator 5 7 having the current of its field 6 controlled by a relay 25 connected to the rectifier 7,'wliich is in circuit with a coil 20 of the alternator. When thespeed of the alternator begins to change the voltage in the coil 20 chan .frcs and therebyT changes the excitation of the field (i, causing a corresponding change in the voltage of the generator 5 and varying the magnetic saturation of the magnetic cores of coils 40 I thus changing the t1 7 E H voltage on the motorprimary and regulating its speed. f l

The primary l is tied to the primary 101 through a tie switch 17 as shown. thus placing them directly in parallel and providing for equal excitation.

The secondary Speed is regulated genere-lly by running rlieoe'ets ll and Changes in 'tlie load during keying rre eomoeneeted for by the eonipeneetifug rlieoetfite lil controlled by relays 13 Wliieli ore connected to tlie -Keying Circuit in manner Well. known in the nrt.

The niotor eeeonduriee ere tied together through the tie switch i8, thereby causing substantially equal mie-ede or tlie seeoiuluriee. In eeeli line of enel niotor Secondary ie eenneeted ureeietenee il-7 l5 or 'lG ahead of tbe tie circuit, Wliieli, oltliougrli it liefe the elleet of reducing; tbe sn/nclironi',zinkrjfl torque` also lios tlie e'l'liect et eeueiiu e comparatively equnl synelironieine torque in ull posi one 0i' the motor seconde 'Il'iese resieteneee,

l therefore, have 'ilie eneet of preventing; the

development ol: torque lierrnonics Wliieli would tend to induce hunting; und provide for steady operation et tne motore und, therefore, of tlie alternatore.

The System di cloned ie obviously adapted to inuny modifiez: ione wliieli would readily suggest tlien'ieelvef' l r one e tiled in the eilt. It Should. therefore, be considered merely 'in un exemplary sense enel not in u limiting; one.

Wliut I cleiin is:

l. In a. radio sien ellingr eyetein, en antenne, e plurality ol esc l ation i.generating' means l L purellelly connected thereto for Supplying energy to seid u tenne, e plurality of the parollelly eo idu'ztion motors o'l" like characteristics for l, lividuzilly driving` seid eene/intere. ene roi Connecting the stator elements of sind motore in ioeiollel. ineens for Connecting tbe rotor elements of seid motors in perulleL edjueteble keying; resistnnces in Ptlie rotor circuits conmion to all et seid inoein, ou antenne, zi.

plu elitv Jilrfii'iion generating ineens perellelly Coupled tli retV for eupnlyingf energy to seid antenne sijmlze,in7 :i plurality of pornllelly Connected induction motore eeeli ot like elioreeteiz, -ee for iin riduolly drivineV Seid generatore in Syneliro eine :i yoriuble reeetuuee in il?,` stator cireuit ot eeeli 0- tlie etzltor e ol' seid motore. ineen incline Yfor tying); t-lte roi' eine, motore together, e veriuble l tence in tlie tie eireuit between Suid rotor el,einent: Suid lreyingr reeie'l noe beine; common eueli ot s 1n otors1 oud e Dlurulity el ifi tied eineotlrinnv reeistnnees olf equal velue inz'liyiduel to eeeli o'l seid rotor circuits: for reducing Circulatingcurrent flowing between the seid rotor elecuit, e pluolity oil. oseillution gene ne' niernfs pnrellelly commented tlm :unl

adopted to supply ene" y to smid losnl ffirei. il, u plurality of purnllelly connected i uetou motore of like eliuineteri` ice iior individuel ly dri fing seid rg'eneietoie,7 e noir et tie eir cuiteI between .Suid induction inou'ueg inenne in one of Seid tie eireuite for dunrgiingf; bunting oscillations in Seid motore und menne iu Seid other tie circuit oiieruted by Suid oseillution `rene siting inem e 'for controlling4 tlie speed oit Seid ino irre.

1l. In e. signalling); system, :i loo d circuit, i plu ality of oscillation ejenerl tin o; ineei'ii-s lieving their outputs pnrollelly eeiigiled tr reto for eupplyinn energy to seid lood circuit, ft plu fulity o'lE driv'ire; meu is 'for individually driving` Seid gener tors, menne in tlie output ot for affecting' ite individuel drivingf ineens; und the driving` ineens el eueli et s l other oeeillution generating; ineens, e tie rcuit lieto-een :ill ol Seid driyiuo; ineens: sind ine lil tie circuit 'for ii'isrinlifiiningf tl'ie infiltofe:L plied by Seid oeeillution Qjeuora zo Suid .lood circuit in lilc i 5. In u. signalling' eyete )mir of oscillation generi' pli; difioiieliip. u. e, leed oireuit their outputs perollelly coupled thereto For eicuit. n ionir l elli? driving):

supplying' energy to Seid lood oit induction motore ilfor indivi d generatore, menne in the outnut oli eueli el seid enerejljf Soureee 'For Pellet-,tine (li-ii:- ingi motor :ind tlie driving' motor oit lie other generator, n tie circuit between seid induction motore ond ineens in Seid tie circuit for rimintoininq tlie voltegee ei pnlied by Suid generleource for energizing? Suid im :i nlurulity ot Saturation coilsy i i eireui l,

Seid energifxiu ol source1 niegue for yoryinp; the

Saturation oli Suid voile eoinnrieine; :i 'plurality oit current .Gouines` reley eircuite emo- Ci'eted therewith tor controlling' "Jie current output of Suid eoureee end ineoi Continollml by seid oscillation noneretinff n for routi'olline' Seid relay cir fuite,u

JAI/IES Il. llIllll-I.

eeoli of Suid oeeilllition generating; menne e to said lood circuit in lille iolizufe relu- 

